1. Field of the Invention
This invention relates to a print system for forming an image on a web using a plurality of printers and in particular to registration control of the print start position in the second or later installed printer.
2. Description of the Related Art
As a print system for forming an image, etc., on both sides of a web typified by belt-like paper continuous in the length direction, a print system is proposed and is commercially practical wherein two printers are placed in series and the printer at the preceding stage (first printer) prints on the first side (surface) of a web and the web ejected from the first printer is reversed to the back by a reversing unit and then is fed into the following printer (second printer) for printing on the second side (back) of the web.
Two types of webs used with such a print system, continuous forms paper comprising sprocket holes in both margins and a web with no sprocket holes, are available, and a print system compatible with both types of webs is becoming pervasive.
In this kind of print system, hitherto the worker has performed work of registering the web placed in the second printer at the print start position by setting a register mark, etc., printed at web perforation or the page top position to a registration gage placed in the printer by visually check.
By the way, generally the printer for handling this kind of web is provided with a tension giving mechanism for giving constant tension to the web in a transport passage of the web. Various configurations of the tension giving mechanism are also proposed. As one of them, hitherto the configuration wherein a plate-like member supported rockably, which will be hereinafter referred to as buffer plate, is placed on the web transport passage and the buffer plate is urged to one side of the web so as to give constant tension to the web is known.
Hitherto, in a print system using a printer having such a buffer plate, the position of the buffer plate (rotation amount) at the completion time of registration of the print start position has not been guaranteed. If print is started in a state in which the buffer plate is positioned above or below the appropriate position, the printer attempts to correct the position of the buffer plate to the appropriate position (neutral position) and executes speed control of each transport mechanism and thus the image at the print start stage may be disarranged.
Thus, hitherto, after completion of registration, the worker has needed to check the position of the buffer plate and adjust to the position of the buffer plate to the appropriate position before starting print; intricate work has been indispensable.
It is an object of the invention to provide a print system and a registration control method at the print start time of the print system capable of automatically performing web print start registration and buffer plate registration and printing an image precisely starting at the first print page.
To the end, according to the invention, there is provided a print system having a first printer for forming an image on a first side of a web and a second printer being placed at the stage following the first printer for forming an image on a second side of the web, the first printer having at least mark formation means for forming a register mark at a predetermined location of the web and the second printer having at least mark detection means for detecting the register mark and a buffer plate being placed so that it can be advanced to and retreated from a web transport passage for giving a constant tension to the web, characterized by control means for setting the buffer plate to a predetermined position during the period until the register mark is transported at a constant distance after passing through the mark detection means.